Lithium carbonate recovery from brines using membrane electrolysis

Abstract

The increased demand for lithium salts puts pressure on the available production capacity. The current technology for lithium extraction is highly time consuming and has raised great concern because of the evaporation, on average, of 500 m3 of water per ton of lithium carbonate. We propose a new technology based on membrane electrolysis to crystallize lithium carbonate from lithium-rich brines. Brine that has been previously deprived from divalent cations and reduced in Na+ concentration, is introduced in the middle compartment of a three-compartment electrochemical reactor. This compartment is separated from the anolyte and catholyte by an anion and a cation exchange membrane, respectively. When a current is applied, anions and cations selectively migrate into the anionic and cathodic compartments, respectively. Water reduction increases the pH of the catholyte, which is recirculated in a crystallizer where CO2 is bubbled and converted to carbonate, precipitating Li2CO3 with a purity of at least 93.8 wt %. Current values ranging from 10 to 100 A m−2 were applied, producing cell voltages from 2.5 to 30 V (highest values correspond to end of batch experiments). The method allows to recover as much as 90% of the volume of the lithium containing solution as low salinity water, with up to 99.7% less total dissolved solids than the processed brine, in marked contrast with current practice. In a non-optimized electrochemical reactor, designed for proof-of-concept experiments, the energy consumption for the electrolysis was calculated at 70.6 kWh m−3 of treated brine.